Instead of a demo I would suggest some free multiplayer weekends with set decks and playing only against people who are playing the free weekend.
That's no good to my target audience. Men between 30 and 40 who have family do not have free weekends, they're with kids and missus. They can maybe steal a few hours on weeknights towards this purpose, which is why a demo is better. The price is no issue, the free time needed to play is, and a demo is essential towards convincing them that you can finish a scenario in an hour and that the game is actually fun during that time.